Precamp breakdown: OL

The Raiders’ offensive line hovered at the so-so line most of last season. Yes, the run blocking was stellar but the pass protection ranged from acceptable to just awful at times.

Penalties were as common as sacks at the tackle positions in particular, making life much more difficult for quarterback JaMarcus Russell than it needed to be.

If Russell and the vertical passing game are to thrive this season, he will need time in the pocket for routes to develop. In other words, as the offensive line goes, so goes the entire passing game.

Here are the five men charged with making that happen.

Projected LT starter: Mario Henderson.

He went from unplayable at midseason — they all but begged Henderson to end the Kwame Harris project to no avail — to much improved in the final two weeks. They did not draft a left tackle because Al Davis wants Henderson to be that guy. They had better hope it works.

If not, Khalif Barnes is there to try and save the day. He will get to compete for the starting job in camp but will have to clearly outplay Henderson to get the nod.

Projected LG starter: Robert Gallery.

The former No. 2 overall pick has finally come into his own as a left guard in the zone-blocking scheme — amazing what a little continuity can do for a former can’t-miss star. This is by far the one line position of least concern. Mark Wilson is the leading backup.

Projected C starter: Samson Satele.

For all those glad to see Jake Grove leave, don’t be so sure the Raiders improved just yet. The tried like buts to re-sign Grove, who ended up with Miami — which then traded Satele to the Raiders because Bill Parcells didn’t think he was better than Grove.

Grove’s biggest downside was his lack of size — and Satele is no bigger to handle Jamal Williams when the Chargers come to town. Satele does, however, possess the prerequisite athleticism desired in the ZBS. Plus, he’s got far better knees than Grove. John Wade is destined for a second-year of backup duty.

Projected RG starter: Cooper Carlisle.

The veteran continued to be the least-penalized lineman but started to show his age in pass protection during the second half of the season — though he had to help out the center more than a few times on top of his own guy. Cable didn’t care: he saw to it that Carlisle was re-signed for a third year. Paul McQuistan and Chris Morris are backup options.

Projected RT starter: Cornell Green.

Then again, maybe not. Green simply was not that good last year with too many penalties and pass-protection problems. Whoever loses out at left tackle — be it Henderson and Barnes — would be considered an upgrade on this side.

Little is known of newcomer Erik Pears. Camp will tell if he’s a viable option. Marcus Johnson is another name to consider.